Increasing animal research has resulted in a corresponding elevated burden on research and caretaking facilities. They have been forced to rethink ways to maximize the animal housing capabilities of existing areas as one way of holding the line on the concomitant increase in expenses attending this expanding research. How to provide for the increasing numbers of animals in limited space, doing everything possible to restrain increased costs--that is the challenge.
Of course, the humane treatment of the animals cannot be sacrificed to accommodate the bottom line. As such, cage manufacturers are guided in their designs by the standards publication for the industry, Guide for the Care and Use of Laboratory Animals, issued by the U.S. Department of Health and Human Services. This document sets various standards for cage size for commonly used laboratory rodents. One such size measurement, critical to space allocation is the floor area/animal.
Lab Products, Inc. of Seaford, Delaware developed a system that efficiently accommodated more rodents per cage in their "One Cage" system. Each cage provided at least an 80 in.sup.2 floor area which accommodated five adult mice over 25 grams according to the Guide standards. However, their specific design required use of new cage accessories including the wire lids and microbarrier tops.
Allentown Caging Equipment of Allentown, N.J., developed their "JAG.sup.75 " cage which it is represented meets the Guide requirement of 75 in.sup.2 for accommodating five adult mice over 25 grams. Allentown relies on the placement of a jag in the sidewalls of the cage. This results in two-section, walls with the bottom section wider or thicker than the top section. The jag as described would appear to enhance the failure possibilities of the cage during manufacture and especially when subjected to higher temperature autoclaving. Further the jag is aesthetically unsightly and provides a ledge where undesirable materials can easily lodge but not as readily be dislodged. Still further, subsequent to its introduction in the market place, it appears that it does not stack all that well. Apparently the minimum amount of clearance gained between the top wall on one cage and the bottom wall of the unit on top is insufficient to permit ready separation, once stacked. It is believed that the so-called "JAG.sup.75 " cage is described in U.S. Pat. No. 5,894,196.
In the '816 patent, Allentown's inventors interpret the Guide standard of 75 in.sup.2 as being practically implementable at a 0.5 inch height above the floor surface due to the presence of animal bedding which would consume this 0.5 inches (see col. 4, ls 24-34). For purposes of the present invention this pragmatic approach is also assumed.
In the '816 patent, at column 5, lines 11-14, the inventors indicate that "[i]t would not be possible, however, to obtain the desired increase usable floor space while maintaining compatibility with prior art top covers by adjusting the taper of the walls and the radius of curvature alone." The present invention, utilizing its innovative mold release techniques, does achieve the necessary compatibility with existing top covers and accessories by in fact changing the radii of curvature and the angle of the walls in relation to the cage floor.
The present invention is directed to an improved cage which results from a method for making same which includes an innovative release technique. The improved cage design provides increased floor area at the 0.5 inch height above the floor bottom. The cage's increased area enables the researcher or caretaker to house five mice in accordance with the Guide's interpreted standard for this cage size. The improved cage, and especially the molding release techniques, accomplish this by: allowing the side and end wall angles, relative to the plane of the floor, to approach 90.degree. as closely as is necessary, which, when taken together with a change in the corner radii, achieve a floor area of more than the desired 75 in.sup.2 at the 0.5 inch height. The stacking of the units is also readily achieved while still accommodating existing top lids and accessories.
Through the utilization of mechanical mold release techniques for the first time in the fabrication of the improved cage product of this type, production quantities can be easily produced having less structural stress and surface scratching on the cage walls. This makes the final product cost competitive in this high volume field.
It is therefore a primary object of the present invention to provide an improved animal cage whereby, through innovative fabrication techniques, a product is cost effectively manufactured, in production quantities, which meets the interpreted Guide requirements for increased floor space, while still providing compatibility with existing top covers and accessory equipment.
It is a further object of the invention to provide such an improved cage product that does not introduce additional stress factors in the side and end wall elements of the product.
It is yet another object of the invention to produce an improved animal cage product that through the adjustment of the wall angle and radius of curvature of the walls in relation to the floor of the cage product, the floor area at the floor surface and/or at an imaginary plane above the floor surface can be adjusted to meet applicable standards; and to accommodate existing top covers and accessories, as well as enabling the nesting of the cage products, one on top of each other, for easy storage.
A still further object of the present invention with its innovative mold release technique, is the significant reduction of structural stress that heretofore has been experienced in the manufacture of animal cage products of the general nature of those described herein.